The present invention is related to medical devices and systems, particularly therapeutic ultrasound systems.
Percutaneously introduced catheters having ultrasound transducers thereon can be used to deliver localized doses of therapeutic ultrasound energy to various sites within a body. Such systems are ideally suited for treating or preventing pathological conditions such as arterial restenosis due to intimal hyperplasia.
To achieve a high level of therapeutic effectiveness, a high amplitude of ultrasound vibration is required. Unfortunately, the acoustic output from a conventional transducer design is typically limited by the inherent properties of the piezoelectric material which forms the transducer. Specifically, when operating typical piezoelectric ceramic transducers at high vibrational amplitudes, the ceramic tends to fracture. This transducer failure is caused by the high tensile stresses within the ceramic material during transducer operation, and the problem is exacerbated by the fact that although piezoelectric ceramic materials tend to have high compressive strengths, they have relatively low tensile strengths.
A further problem common to existing catheter-based ultrasound systems is that they lack the necessary flexibility to negotiate tortuous paths through body lumens. This is especially true when such systems comprise a plurality of axially spaced apart ultrasound transducers disposed along the length of the catheter body. In such cases, the catheter flexibility is unfortunately influenced both by the number and size of the conductors that are used to interconnect the various transducers.
A further problem common to existing catheter-based ultrasound systems which use a plurality of ultrasound transducers is the difficulty in individually wiring each of these transducers, since a large number of individual wires leading to each of the transducers typically results in a rather bulky system.